It is a cool poster, so I tracked it down. It's by Max Fyfield, a magazine illustrator active in the 1970's.
Imagine my surprise when I found apparently reputable sources
that said that Euler also endorsed a hollow earth theory, and that Fyfield’s map was based on Euler’s theories.
It is a cool poster, so I tracked it down. It's by Max Fyfield, a magazine illustrator active in the 1970's.
http://eulerarchive.maa.org/hedi/HEDI-2007-04.pdf